1. Field of the Invention
The present invention relates to a circuit device and a method of manufacture thereof and particularly relate to a circuit device, with which separation grooves having constricted parts at side surfaces are formed by performing etching a plurality of times on a copper foil to form the separation grooves and the transient thermal resistance is restrained by forming conductive patterns thickly, and a method of manufacture of such a circuit device.
2. Description of the Related Art
Conventionally, due to being employed in portable telephones, portable computers, etc., circuit devices that are set in electronic equipment have been demanded to be compact, thin, and lightweight.
Recently, as general semiconductor devices called CSP's (chip size packages), wafer-scale CSP's of sizes equivalent to chips and CSP's of sizes slightly larger than chips have been developed.
FIG. 14 shows a CSP 66, which is slightly larger than a chip size and employs a glass epoxy substrate 5 as the supporting substrate. Here, a description shall be provided for the case where a transistor chip T is mounted onto glass epoxy substrate 65.
On the surface of this glass epoxy substrate 65, a first electrode 67, a second electrode 68, and a die pad 69 are formed. A first rear surface electrode 70 and a second rear surface electrode 71 are formed on the rear surface of this glass epoxy substrate 65. Via through holes TH, the abovementioned first electrode 67 is electrically connected with first rear surface electrode 70 and second electrode 68 is electrically connected with second rear surface electrode 71. The above-mentioned transistor chip T is affixed in bare form onto die pad 69, the emitter electrode of the transistor is connected via a metal wire 72 to first electrode 67, and the base electrode of the transistor is connected via a metal wire 72 to second electrode 68. Furthermore, a resin layer 73 is provided on glass epoxy substrate 65 so as to cover transistor chip T.
Though employing a glass epoxy substrate 65, the abovementioned CSP 66, unlike a wafer-scale CSP, has the merits of being simple in the extension structure from chip T to the rear surface electrodes 70 and 71 for external connection and being inexpensive to manufacture.
However, the above-described CSP 66 uses a glass substrate 65 as an interposer and this places on limit on making CSP 66 more compact and thinner. A circuit device 80, with which such a mounting substrate is made unnecessary as shown in FIG. 15, has thus been developed.
As shown in FIG. 15, circuit device 80 comprises conductive patterns 81, circuit elements 82 affixed onto conductive patterns 81, metal wires 84, electrically connecting circuit elements 82 and conductive patterns 81, and an insulating resin 83, covering circuit elements 82 and conductive patterns 81 while exposing the rear surfaces of conductive patterns 81. Circuit device 80 is thus arranged so that a mounting substrate is unnecessary and is formed more thinly and more compactly in comparison to CSP 66.
However, with the above-described circuit device 80, conductive patterns 81 are formed thinly and have a thickness of only approximately 40 μm, and since this causes increase of the transient thermal resistance, there was the problem that temperature rise of circuit device 80 occurs quickly due to heat generation by circuit elements 82. Also, if thick conductive patterns 81 are formed by forming separation grooves by a single time of etching, the separation grooves are formed to be wide in width, causing decrease of the effective area in which conductive patterns 81 are formed.
Furthermore, though side surfaces of conductive patterns 81 are formed to a curved form due to conductive patterns 81 being formed by etching, the adhesion with insulating resin 13 was not adequate and there was the problem that conductive patterns 81 peeled off from insulating resin 13.
This embodiments of present invention has been made in view of the above problems. One of objects of this embodiments of present invention is to provide a circuit device, having conductive patterns that are formed thickly in order to make the transient thermal resistance small, and a method of manufacturing such a circuit device. Another object of this invention is to provide a circuit device, with which the adhesion of an insulating resin with conductive patterns is improved by the provision of constricted parts at side surfaces of separation grooves that separate the conductive patterns.